The correct preposition to use in the sentence "I did not see you _____ the office party." is "at." Prepositions in English can indicate temporal or spatial relationships. In this context, we are discussing the location of an event, namely the "office party." The preposition "at" is typically used when referring to specific locations or events, such as "at the office," "at the party," or "at the meeting."
The other options do not fit correctly in this context:
- "in" is generally used for enclosed spaces or countries and large areas, like "in the room" or "in France," not for specific events.
- "for" is typically used to indicate purpose or duration, which does not suit the sentence structure here.
- "on" is often used with days or surfaces, like "on Monday" or "on the table," but not for specific events.
Therefore, the best choice is: at.